Lens system for terrestrial telescopes



C. S. HASTINGS.

LENS SYSTEM FOR TERRESTRLAL TELESCOPES.

Patentd Nov. 1, 1921.

UNITED STATES PATENT OFFICE.

CHARLES s. HASTINGS, O'FNEW HAVEN, oonnnorrcu'r.

LENS SYSTEM FOR TERRESTRIAL TELESCOPES.

' Application filed, July 10,

To aQZ whom it may concern:

Be it known that I, CHARLES S. HASTINGS, a citizen of the United States, residing at New Haven, in the county of New Haven and State of Connecticut, have invented a new and useful Improvement in Lens Systems for Terrestrial Telescopes; and I do hereby declare the following, when taken in connection with the accompanying drawings and the characters of reference marked thereon, to be a full, clear, and exact description of the same, and which said drawings constitute part of this application, and represents a diagrammatic view of a terrestrial telescope lens computed in accordance with my invention.

y invention relates to an improvement in optical lens systems for telescopes. The obj ect of my invention is to produce a telescope of the terrestrial type with especial reference to the use of the said telescope as a sight for rifles.

A telescope for such purposes must deviate in certain important respects from the ordinary terrestrial telescope. It must be short, light in weight and small in diameter, since it is to be mounted upon a rifle; it must have 'a long eye distance, so that the recoil of the arm may not bring the eye piece in contact with the eye; it must have a large field of great brilliancy and wide angle; and it must be initially adaptable to a considerable range of magnification.

With these ends in view, my invention consists in a telescope of the type described, characterized by having a complex objective of short negative focal length and an ocular of positive focal length. My invention further consists in a telescope of the character described having certain details of design and construction as will be hereinafter described and pointed out in the claims.

11 carrying out my invention, as herein shown, I employ a sequence of nine lenses, grouped for purposes of computation in two groups, the first consisting of three cemented doublets which, as a system, compose my complex objective of short negative focal length; the second group consistin of asingle lens followed by a cemented doublet; these composing my ocular system of positive focal length. 7

In the prior art it has been customary to compute terrestrial telescopes of this type in Specification of Letters Patent.

1920. Serial No. 395,287.

either of two ways, both differing from my improved construction. Such telescopes have from one point of view as conslsting of an objective system, an inverting system and an ocular system and in the computation of the lenses for such 'a telescope, each. of these systems has been computed so as to be as nearly optically correct and free from aberrations and other optical errors as possible. From another point of view such telescopes have been considered as consisting of a simple objective of positive focal length followed by an ocular which is fleet a compound microscope; each of these two co-acting systems being computed so as to be optically correct in itself.

I am enabled to so proportion the lenses of my system that my six-lens objective system aving a short negative focal length,"although composed of subordinate systems which are themselves optically faulty, is itself free from optical errors and when combined with my improved ocular. system, which has a positive focal length, will pro duce a telescopic system having all of the advantages desirable for the purposes set forth and especially characterized by the fact that I am enabled to employ satisfactorily, rays of light deviating four times as far from the optical axis as was the case in any previous system having as small a number of lenses as I am enabled to employ.

In practising my invention, as shown in the accompanying drawing, the lenses 2, 3, 4, 5, 6 and 7 are the components of my compound objective of negative focal length and the lenses 8, 9 and 10 compose my ocular system of positive focal length. The lenses numbered 2, 4:, 7 and 10 are formed from a glass known as, dense optical flint having an index of refraction N :1.61655 and the lenses numbered 3, 5, 6, 8 and 9 are formed of a glass known as heavy crown, having an index of refraction N :1.52472. The light incident upon the system is supposed to fall upon the outer surface of the lens 2 and to emerge from the system at the outer surface of the lens 10. Thus the direction of the light propagated through the system is from left to right and for purposes of computa- Patented Nov. 1, 1921.

V s a; unitary system. By

consisting of ing as methods.

tion, as is customary, this direction/is assumed to be positive; the contrary direction thus becoming negative.

The radii of curvature of the successive surfaces beginning with the left hand, or outer surface, the dimensions being given in inches, and each radius being measured from the surface toward the center: r,=2.170,r,=0.686,r,='

-2.5s5, r,= w, 1' =0.945, 1,: -1.115 15: 1.115, r,,= 0945,1 a, 1', =6.000, r 1.000, r,,=. 1.081, r 0.-625, T -a793.

The th'cknesses of the successive lenses in the-same order are as follows:t,=0.060 t',=0.130, t,'=0.060,- t,-0.060, t,=0.130, t,=0.268, t,=0.050.

the separations are as follows:-s,=

5.220, s, =0.29s, s 3.220, s, 0.570

focal lengths of With these constants the the successive units (2, 3), l, 5), (6, 7), (8), (9, 10) are approximately +2.83, +2.64", +2.64", +1.64", +2.01 respectively, the focal length'of the complex sixlens objective is approximately 2.86" and the focal length of the three-lens ocular is approximately +1.08.

The objective, namely the system com- 5, 6, and 7 is com-- posed of the lenses 2, 3, 4, puted'as a unit to eliminate asfar as possible the optical errors; particularly distortion of the field, curvature of the field, astigmatism in the field, spherical aberration, chromatic aberration and chromatic difference of magnification.

In the same way the I ocular system', composed of the lenses 8, 9

and 10, is computed this, method of treatment, I produce at'elescope system com posed of a six-lens objective of negative focallength which as a unit is optically correct, but in which he anterior doublet 2-3 or the posterior pair of doublets 4-5 and 67 are not optically correct but compensate each others' errors and could not be replaced by optically correct focal length.- 1 is l An added advantage due to this mode of grouping of the lenses is that I am enabled to vary the distance. from the lens '3 to the lens 4 to a considerable extent, thus initially changing the magnification of the teles co e through a comparatively large range lenses of equal wit out harming the character of the imagleilproduced by thecomple'x objective.

oreover, I am enabled by this manner of grouping the lenses to utilizev an ocular three lenses, namely a' only single field lens and a doubleteye lens 1n place of the customary sary in telescopes-' computed by the older Thus my telescope is characterized'by havof the lens 2 are, as follows,

the focal length is "positive or negative,

of three cemented doublets, ocular system of'positive fojca li'length, conf 'sisting of a field'lens and cemented' doublet V doublets of both the-said I or '5 lens combina-f tion which has hitherto been found neces- V a. complex ob ective system of short, negative, focal length which caImOt be separated .into individually optically correct objective and inverter systems, butin which on the other hand, the component lenses and combinations of lenses arein themselves optically faulty, forming compensating effects.

My telescope is further characterized by having an ocular system of positive focal length and composed of only three lenses.

The final adjustment of the spherical aberration of the system is made by Varying the ratio of theradii of curvature of, the surfaces of the ocularfield-lens and I have discovered that the use of different varieties of glass'will also compel a change in; this ratio. characterizedbythe fact that this ratio will have Values ranging from 9; to @inclusive.

.The dimensions given herein may be varied as required by the optical qualitie of the glass available at any g'ven time for useand also by the precise values of the I .find that my telescope system 1s as 2 and-3 or thej positivefocal length, the said objective and the said ocular being positive focal length only. 7

2..An opticalsystem for telescopes concomposed of units of sisting' solely of a complex objective of nega- I tive focal length and positive focal length, the aid objectiveand .the'said ocular-being composed of units of positive focal length only,

. the said units of the sa1d objective system a complex ocular of being collectively.

adjusted. to minimize spherical and chromatic aberrations.

3. A telescopehavlng a eo'm exj objective system of negative focal length, consisting and a complex eye-lens, the said systems and the said fieldlens of the said ocular system being. each of positive. focal system of negative focal length,- consisting.

, of three cemented doublets, and a complex I. '4. A telescope having a complex objective ocular system of positive focal'length, con SlStlIlg. of, a field lens and cemented doublet eye-lens, the said doublets of both the saidsystems and the'said field lens'of thesaid ocular system being each of, ositi've focal.

iao

length, the said objective system bein collectively adjusted to correct distortion in the field, curvature of the field, astigmatism of the field and chromatic and spherical aberrations.

5. A telescope objective of short negative focal length, consisting of three cemented doublets each of positive focal length, yield- 111g two interior real images each of these images being separately corrected for chromatic and for spherical aberrations at the axis.

6; An objective approximately cemented achromatic doublets, each comprising a lens of flint lass, N 1.616, and a lens of crown glass, l\ 1.525, the successive surfaces of the system having the following radii of curvature:r =2.17 in., r, 0.69 in.,1' 2.54 in., r,= co, r =0.95 in., 1',= 1.12 in., r,=1.12 in., r 0.95 in., r,= co

7. An ocular of approximately 1.08

of negative focal length of positive focal length of in., composed of a simple -2.86 in. composed of three crown lass (N =1.525) lens and a cemented doublet of crown glass (N 1.525) and flint glass (N =1.616), the successive surfaces of the system having the following radii of curvature:r =6.00 in., r 1.00 in., r, =1.08i11., r 0.63 in., r 3.79 in.

8. A system comprising the system of claims 6 and 7.

9. A telescope ocular of positive focal length consisting of a cemented doublet eyelens and a biconvex field-lens, characterized by the fact that the radius of curvature of one of the surfaces of the said field-lens is from four to eight times as great as the radius of curvature of the other surface thereof.

In testimony whereof, I have signed this specification 1n the presence of two subscribing witnesses.

CHARLES s. HASTINGS;

Witnesses:

DANIEL H. VEADER, ERIK S. PALMER. 

